Airbags are almost a standard fixture in vehicles of recent years. An airbag is a safety apparatus that operates during an emergency such as a vehicle collision, and inflates and deploys due to gas pressure so as to restrain and thereby protect an occupant. There are various types of airbag apparatus, which vary according to installation location and application. For example, in order to protect an occupant of a front seat mainly from an impact in a front-rear direction, a front airbag is provided in the center of a steering wheel in front of a driver seat, and a passenger airbag is provided in an instrument panel or another area in the vicinity of a front passenger seat. In addition, in order to protect occupants in front and rear rows from a side collision and subsequent rollover (overturn), a curtain airbag, which inflates and deploys along a side window, is provided in the vicinity of a roof, and a side airbag, which inflates and deploys immediately beside an occupant, is provided in a side portion of a seat.
The airbag arrangement structure disclosed in Japanese Patent Application Publication No.: H06-80057 can also be adapted for front seats accommodating three people. In accordance with this reference, a third airbag unit for restraining an occupant of a center seat inflates and deploys in addition to a first airbag unit for restraining an occupant of a driver seat and a second airbag unit for restraining an occupant of a front passenger seat. The third airbag unit is installed in the vicinity of a sun visor on a ceiling, and inflates and deploys in a downward direction between the occupant of the center seat and an instrument panel.